/Engine/Plugins/Runtime/MassEntity/Source/MassEntity/Public/MassObserverManager.h
bool OnPreEntitiesDestroyed ( [FMassProcessingContext](API\Plugins\MassEntity\FMassProcessingContext) & ProcessingContext, const [FMassArchetypeEntityCollection](API\Plugins\MassEntity\FMassArchetypeEntityCollection) & EntityCollection )